This invention relates to a detector with a titanium sapphire laser as a pumping light source the laser beam of which can be continuously changed in wavelength.
There have been proposed a variety of detecting or measuring devices based on an optical method for instance in the field of analysis.
Examples of the detecting or measuring devices are a high speed liquid chromatography fluorescence detector, and a variety of Raman measuring devices. These detecting or measuring devices have been widely employed as means for quantitatively analyzing biological specimens such as physiological active substances with high accuracy, means for studying the structures of biological substances, means for analyzing the crystalline configurations of solid substances, and so forth for instance in the field of medicine or in the field of biochemistry.
It is practically essential for the above-described detecting or measuring devices based on the optical method to have an exciting light source which is capable of emitting a light beam whose wavelength matches the responsive wavelength band of a component under test. Most of the commercially available lasers are so designed as to emit laser beams having wavelengths which are inherent in them, respectively. Examples of such lasers are an Ar laser (488, 515 nm), He-Ne laser (633 nm) and copper vapor laser (511 nm) provided as gas lasers, and a YAG laser (1064 nm) and a semiconductor laser (780, 830, 1300, 1550 nm) provided as solid lasers.
However, these lasers are not always practical in use. The Ar, He-Ne, copper vapor and YAG lasers are discrete or discontinuous as was described above. Hence, if, in the case where any one of these lasers is employed as a light source, the response wavelength of a component under test is different from the wavelength of the laser beam, then the component cannot be tested. Even if it could be tested, the test would be considerably low in sensitivity. The same thing can be said to a semiconductor laser whose wavelength can be changed in a range of several nanometers (nm).
A dye laser is variable in oscillation wavelength, and its wavelength can be matched with the response wavelength band of a component under test. However, the dye laser is disadvantageous in that the dye is deteriorated by light during operation, so that the laser oscillation output is varied; that is, the dye laser is unstable in operation, and furthermore the dye laser is relatively short in service life, and its maintenance is rather difficult.
Frequently, the absorption spectrum of a specimen is different from the wavelength of the laser. Accordingly, in the case where such a laser beam source discrete in oscillation wavelength is employed for a detecting device such as a high speed liquid chromatography fluorescence detector, it would be difficult to perform even an analysis of the order of pico-grams. Therefore when it is forced to perform the analysis with high sensitivity, analysis, intricate operations must be carried out; for instance in measurement of a fluorescent spectrum, the specimen must be made fluorescent by chemical treatment. Even if the specimen is made fluorescent, it is difficult to give a high sensitivity analysis of the order of "femto (10.sup.-15) grams" to it. From the spectrum of the output light of an Xe lamp, light is obtained in a wide range of from about 220 nm to about 1000 nm; however, the light is weaker than the laser beam, and accordingly it is difficult to perform a high sensitivity quantitative analysis with the output light of the Xe lamp.
In the case of a Raman measuring device incorporating such a laser, it is difficult to stably and readily measure the Raman spectrum of a specimen under test at all times.
Thus, the conventional devices suffer from various problems.